This invention relates to gasoline engines and more particularly, to an engine starting system for internal combustion engines.
Conventional boat engines are typically provided with either a pull-start system or a starter motor. In the pull-start system, the user starts the engine by pulling on a rope coupled to a crankshaft. The starter motor is typically connected to an on-board battery, which initiates rotation of the crankshaft and starting of the engine. Batteries are typically large; they occupy valuable space on the boat. With pull-start systems no batteries are required.
It is well known that two-stroke engines are more powerful that four stroke engines of equivalent size. Two-stroke engines fire once every revolution, while four-stroke engines fire once every other revolution. This gives two-stroke engines a significant power boost. Such engines are lighter and simpler in construction. Small power tools, outboard motors, jet skis, light motorcycles and the like have all employed two-stroke engines. Unfortunately, most two stroke engines are inefficient and are highly pollutant due to the amount of unspent fuel that escapes through the exhaust port.
The industry has developed a two-stroke low pressure direct injection system (TLDI) such as for instance Nissan/Tohatsu injection system. This system was designed to make two stroke outboard motors meet emissions regulations while running on gasoline. The preferred fuel source for Nissan/Tohatsu motor is gasoline although it appears to be capable of running on heavy fuels, such as diesel.
In the context of watercraft, heavy fuel is preferred since it reduces the risk of fire and significantly reduces the amount of harmful exhaust. However, starting a two-stroke motor on heavy fuel is a problem. Sometimes conventional engines will start on kerosene or jet fuel JP-5 using the electric starter but not easily. With a pull rope starter it is not possible. Furthermore, the conventional Nissan/Tohatsu engine with the two-stroke system will not run without a battery. The orbital system uses one fuel injector, one air injector, and one ignition coil per cylinder, and one high pressure fuel pump. Each of these components operates using electricity. This system needs a large electrical supply compared to other known outboard motors. In fact, Nissan recommends a battery with 850 to 1000 cranking amps.
Thus, there is a need for a marine engine having a starter system that alleviates the need for a battery and that can operate on heavy fuel. The present invention contemplates elimination of the drawbacks of prior starter systems for marine engines and provision of a batteryless heavy fuel starting system.